The invention relates to implantable prostheses, and more particularly to components of hip joint prostheses.
The hip joint is a ball-and-socket type joint in which the ball-shaped femoral head is engaged with and articulates with a cup-shaped socket known as the acetabulum. Injury and/or disease may damage the hip joint to the extent that it must be replaced by or augmented with a prosthetic joint. Deterioration of the acetabulum, and particularly the cartilage within the acetabulum, requires that a prosthetic acetabular shell be mounted within a prepared area of the acetabulum. The acetabular shell receives and articulates with a prosthetic femoral head which is installed on a proximal portion of a patient's femur.
In some instances, degenerative bone conditions deteriorate the acetabulum, and particularly its medial wall, to the extent that the acetabulum does not have the integrity to serve as a mounting platform for a prosthetic acetabular shell. This condition requires a reinforcement prosthesis which is implanted within the acetabulum before the acetabular cup, and at least a portion of which receives the acetabular cup. Such a reinforcement body, sometimes known as a protrusio cage, includes a main body that is at least partially cup-shaped and which includes two or more integral radially extending flanges. The protrusio cage is first stabilized within the acetabulum using bone cement or bone screws. Thereafter, the flanges are joined to the ilium, ischium and pubis to further secure the cage and to distribute forces away from the medial wall of the acetabulum. An exemplary protrusio cage is further described by Oh et al., Clin. Orthopaedics and Related Research, No. 162, pp. 175-184 (1982) and by Schatzker et al., Arch. Orthop. Traum. Surg., Vol. 103, No. 1, pp. 5-12 (1984). U.S. Pat. Nos. 4,437,193 and 4,623,352 also describe exemplary protrusio cages.
While known protrusio cages can be useful, they are often difficult to install in an ideal manner due to natural anatomical differences among patients as well as anatomical differences resulting from different disease and/or injury conditions. Because of these anatomical differences, the fixed flanges of known protrusio cages must be manipulated and/or altered, during surgery, to properly install the protrusio cage. Even with such manipulation and alteration, the protrusio cages still may not be optimally implanted within some patients.
Accordingly, there is need for protrusio cages, or similar acetabular reinforcement bodies, that can be more easily installed by surgeons during hip arthroplasty procedures to accommodate the varying anatomies of patients.